Even in fiction, there are drugs and substances that impact the lives of heroes. These substances are often double-edged – some of them give you power and others save lives, but still others are addictive and destructive.
In many ways, the substances and drugs of fiction mimic the ones in our real world. They also serve as a representation of how our society views drugs and drug culture. Moloko Plus is a cocktail that murderers and psychopaths drink before going on violent rampages. Plasmids give you super powers, but they're also highly addictive and gradually rot your mind. Melange gives you long life, but also makes you so addicted that you would die without it. The benefits are rarely worth the sacrifices. Some fictional drugs are more like medicine, and are healthy in small doses. But like in the real world, over-use of anything is often fatal. Even in a video game, just say no to drugs!